1. Technical Field
This application relates to mobile telecommunications systems in general, having particular application in UMTS (Universal Mobile Telecommunications System) in general, and in particular to an apparatus and method for applying ciphering in universal mobile telecommunications system.
2. Description of the Related Art
The approaches described in this section could be pursued, but are not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
In a typical cellular radio system, mobile user equipment (UE) communicates via a radio access radio network (RAN) to one or more core networks. User equipment (UE) comprises various types of equipment such as mobile telephones (also known as cellular or cell phones), lap tops with wireless communication capability, personal digital assistants (PDAs) etc. These may be portable, hand held, pocket sized, installed in a vehicle etc and communicate voice and/or data signals with the radio access network.
The radio access network covers a geographical area divided into a plurality of cell areas. Each cell area is served by at least one base station, which may be referred to as a Node B. Each cell is identified by a unique identifier which is broadcast in the cell. The base stations communicate at radio frequencies over an air interface with the UEs within range of the base station. Several base stations may be connected to a radio network controller (RNC) which controls various activities of the base stations. The radio network controllers are typically connected to a core network.
UMTS is a third generation public land mobile telecommunication system. Various standardization bodies are known to publish and set standards for UMTS, each in their respective areas of competence. For instance, the 3GPP (Third Generation Partnership Project) has been known to publish and set standards for GSM (Global System for Mobile Communications) based UMTS, and the 3GPP2 (Third Generation Partnership Project 2) has been known to publish and set standards for CDMA (Code Division Multiple Access) based UMTS. Within the scope of a particular standardization body, specific partners publish and set standards in their respective areas.
Consider a wireless mobile device, generally referred to as user equipment (UE), that complies with the 3GPP specifications for the UMTS protocol. The 3GPP 25.331 specification, v.3.15.0, referred to herein as the 25.331 specification, addresses the subject of UMTS RRC (Radio Resource Control) protocol requirements between the UMTS Terrestrial Radio Access Network (UTRAN) and the UE.
In a UMTS UE each radio bearer (including signalling radio bearers) may be configured to apply ciphering to all data as part of the security features of UMTS. Ciphering refers to the encryption or decryption of a ciphering unit (a Packet Data Unit (PDU) or Service Data Unit (SDU)). The 25.331 standard states in section 8.6.3.4 that, at any given time, the UE needs to store at most two different ciphering configurations (keyset and algorithm) per Core Network (CN) domain at any given time in total for all radio bearers and three configurations in total for all signalling radio bearers.
To turn on ciphering in the UE, the UTRAN sends a message (for example a SECURITY MODE CONTROL message as set out in section 8.1.12 of the 25.331 standard) to the UE. On receiving the message, the UE must configure each Radio Bearer belonging to the Core Network (CN) domain with the ciphering configuration. This consists of sending: the Hyper Frame Number (HFN); key; algorithm; and activation time to each Radio Bearer. After this information has been transferred, the UE is able to respond back to the UTRAN (for example with a SECURITY MODE COMPLETE message) informing it that the UE is ready to start ciphering.
The time it takes the UE to respond to the UTRAN request is dependant on how quickly the UE is able to configure the Radio Bearers and will impact on how quickly the system is able to start ciphering and hence apply security protection to the data.
There are proposed strategies for dealing with ciphering configurations. A number of such strategies are detailed below.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of an apparatus and method for applying ciphering in mobile telecommunications system user equipment.
The same reference numerals are used in different figures to denote similar elements.